The present invention concerns extrudable halogen-free mixtures based on polyetherimide polymer.
The use of siloxane-polyetherimide copolymer for improvement of flame-retardance of wires is known, as is the manufacture of insulation or coverings of electrical cables from materials of like flame-retardance (WO 94/27298).
EP 0 417 513 A1 discloses a procedure in which small quantities (0.2-15 weight-%) of a siloxane-polyetherimide copolymer is blended with a polyetherimide polymer for the same purposes. In this case, polyetherimides that are commercially available from the General Electric Company ("GCE") as ULTEM 1000, 5000, and 6001 were used. These were blended with ULTEM D9000, a siloxane-polyetherimide copolymer also available from GEC. The resistance to abrasion of these materials is relatively high, as Is their impact strength. These materials are less well adapted for use in flexible cable applications. Within cost limitations, these materials find broad usage, but their employment has been limited, up to now, to items manufactured by injection molding.
There is currently available, also from GEC, a polyetherimide polymer that can be employed in injection molding as well as for extrusion. This so-called flexible copolymer is available as SILTEM (ULTEM Profile, Introduction, ULTEM Polyetherimide Resins). This resin is characterized not only by its flexibility, but also by its high resistance to abrasion and chemical attack. The high price for this copolymer limits its applications to special areas where cost is of little importance.
According to the information from the manufacturer (ULTEM Profile 3, Product Selection), while the elastic modulus for ULTEM 9075 is 3000 MPa, that of SILTEM is approximately 475 MPa.
As far as the present invention is concerned, in contrast to the teachings of EP 0 417 513 A1, one does not introduce small amounts of siloxane-polyetherimide copolymer as an additive to improve the flame-retardance of a polyetherimide polymer. Rather, the present invention provides a mixture of a polyetherimide polymer with a sufficient quantity of a flexible siloxane-polyetherimide copolymer to improve the workability of the polyetherimide polymer, so that new products can open new areas of application.